Comments on Geologic Parameters

14 Porosity:

Although only limited published information regarding porosity of the Lagarto/Oakville interval is available (Core Laboratories, 1972b; Wallace and others, 1979; Kreitler and others, 1988), most agree that the thicker sand intervals range between 23 and 28 percent porosity. Muddier and siltier sands are more typically 16 percent. To represent porosity in the GIS we used the net-sand map of the lower Miocene (6,150 ft) interval, as mapped by Ambrose (1990), in which we assign a value of 27 percent porosity to the thicker (barrier-island facies) sands and 16 percent porosity to the thinner (barrier-island flank facies) sands. For more detailed analysis of porosity within the Lagarto and Oakville Formations in the Texas City area, geophysical logs from gas and oil wells can be an excellent source of data for determining and mapping porosity distribution.

14 Map:

14 Reference:

Ambrose, W. A., 1990, Facies heterogeneity and brine-disposal potential of Miocene barrier-island, fluvial, and deltaic systems: examples from northeast Hitchcock and Alta Loma Fields, Galveston County, Texas: The University of Texas at Austin, Bureau of Economic Geology, Geological Circular 90-4, 35 p.

Core Laboratories, 1972a, A survey of the subsurface saline water of Texas: Volume 2 chemical analysis of saline water: Texas Water Development Board, Report 157, 378 p.

Kreitler, C. W., Akhter, M. S., Donnelly, A. C. A, and Wood, W. T., 1988, Hydrogeology of formations used for deep-well injection, Texas Gulf Coast: The University of Texas at Austin, Bureau of Economic Geology, open-file report prepared for U.S. Environmental Protection Agency under Cooperative Agreement ID No. CR812786-01, 204 p.

Wallace, R. H., Kraemer, T. F., Taylor, R. E., and Wesselman, J. B., 1979, Assessment of geopressured-geothermal resources in the northern Gulf of Mexico basin: U.S. Geological Survey, Circular 790, 132–155.